Present invention relates to an ink-jet head assembling method and apparatus and more particularly, to a method and apparatus assembling a head nozzle of a printing head which discharges ink, by mounting a top plate member on a heater board formed with a plurality of heaters for heating the ink, the top plate member has a plurality of nozzles corresponding to the heaters.
Conventionally, so-called bubble-jet type printing head, which heats ink to form bubbles when the ink is discharged to be printed on a paper sheet, has been developed and put into practical use. This bubble-jet type printing head is advantageous due to improving printing precision.
In an assembling apparatus for the bubble-jet type printing head, heaters for heating and boiling ink to form bubbles and discharge orifices for discharging bubbles toward a paper sheet must be precisely aligned on the order of microns. For example, in order to attain a printing precision of about 360 dpi (dots per inch), it is necessary to align 64 discharge orifices within a range of about 4.5 mm at a constant pitch, and the alignment is very small, about 70 microns.
For formation of discharge orifices at such a very small pitch, the discharge orifices can be formed with allowable predetermined high precision in an orifice plate to be attached to the front surface of a top plate member by using, e.g., an ultra-high-precision process machine such as a laser process machine. Similarly, heaters can be formed on a heater board with allowable predetermined high precision, by using an ultra-high-precision etching technique.
In a conventional assembling apparatus, a heater board and a top plate member are respectively set using special-purpose jigs so as to align them in order hat the top plate member can be placed on the heater board in a state that each axis of heaters on the heater board and the orifices formed in the orifice plate precisely coincide. Thereafter, the heater board and the top plate member are manually aligned while alternately observing the heaters and orifices using a precision microscope.
More particularly, a set of fingers to clamp the top plate member are arranged at a predetermined distance above the upper surface of the top plate member placed (temporarily placed) on the heater board. These fingers are moved in a lateral direction to engage the ink reception portion and to move the top plate member on the heater board for precisely aligning both arranging positions.
However, in the conventional apparatus, the thickness of a top plate member changes depending upon processing variations and the gap between the fingers and the upper surface of the top plate member changes, causing problems in the alignment of the top plate member and the heater board. When the thickness of the top plate member is rather thick in comparison to a fixed standard, the gap between the top plate member and the fingers is very small and the contact pressure between the heater board and the top plate member increases. This disturbs the motion of the top plate member in alignment, degrading the aligning precision, or making matters worse, resulting in breakage to the fingers. On the other hand, when the top plate member is thin, the gap between the top plate member and the fingers becomes larger than the desired amount. The top plate member is inclined to one side while it is moved in the alignment. In this case, not only the precise alignment cannot be performed, but fingers might pass over the ink reception portion, which makes the alignment impossible.
Another problem is that, in a conventional assembling apparatus, the aforementioned manual alignment of the heater board and the top plate member causes a variation among workers, a variation depending on the degree of skill of each worker, and a variation depending on the degree of fatigue of each worker. These variations impair position adjustment precision, and pose a problem in reliability of the final products. In addition, since visual measurements and manual operations of jigs are repeated, the time required for alignment is prolonged, resulting in a decrease in assembling efficiency caused by the prolonged assembling time. Furthermore, more time is required until workers become skilled.
In the conventional assembling apparatus, after the heater board and the top plate member are aligned, they are temporarily attached in a manner that a discharging needle of an adhesive supply dispenser is manually set toward a joint portion of the heater board and the top plate member, through which an ultraviolet-setting adhesive is applied, and the joint portion applied with the adhesive is radiated with the ultraviolet rays. This temporarily attached assembly is fixed on a base plate via a spring using special-purpose tools. In this conventional manner, the adhesive is delivered from the discharge needle of the dispenser after attachment of the heater board and the top plate member. In this process, the relative position between the heater board and the top plate member may shift.
Further, as the setting of the discharge needle is made by visual measurement, the management of the adhesive apply portion and apply amount is difficult. As a result, if the adhesive apply position and the apply amount are out of balance, joint states may change due to varying contraction in drying of the adhesive. If the adhesive is applied near an ink channel of the top plate member, the adhesive may penetrate into the channel to fill a nozzle hole.
If the adhesive penetrates into the ink channel which should be fixed by springs, the channel may be filled with the adhesive and the ink may not be discharged. The adhesive may further penetrate thru the joint of the top plate member and the heater board to make a gap between the top plate member and the heater board, causing a leakage of the ink between nozzles.
In the conventional assembling apparatus, when the top plate member is mounted on the heater board, in order to hold this top plate member, a sucker attached under the fingers are brought into a sucking state. A worker picks up one of the top plate members from a tray by, e.g., a pair of tweezers, moves the top plate member near to the sucker of the finger member, to have the sucker hold the top plate.
In this manual operation with visual measurement, precise alignment cannot be obtained. Further, the occurrence of variation among workers, and the fear of too much pressing to break the top plate member or the finger member are pointed out.
In the conventional assembling apparatus, one of the plurality of heaters located at the center of the heater board is specified as the reference heater. More specifically, in an image of the heater board photographed by a tool-maker's microscope, within an image area, the heater closest to the center of the image area is specified as the reference heater.
However, even when the heater board is shifted in the x-axis direction due to a shift between the heater board and the base plate or a shift between the base plate and jig clamp, the same heater pattern is displayed within the image area. Accordingly, it is difficult to distinguish heater boards shifted in the x-axis direction.
For the above reason, if a shifted heater board is attached to a top plate member, the heaters are not correctly combined with nozzle holes having corresponding numerals, and they are set shifted by one or more than two holes. As a result, the nozzle hole(s) not being combined with corresponding heater(s) at the end portion cannot discharge ink.